Commentaires 0

Retranscription de la présentation

Fundamental Concepts:Fundamental Concepts:SedimentationSedimentationAnn KenimerAnn KenimerTexas A & M UniversityTexas A & M UniversityUniversity Curriculum Development forUniversity Curriculum Development forDecentralized WastewaterDecentralized WastewaterManagementManagementNDWRCDP DisclaimerNDWRCDP DisclaimerThis work was supported by the National Decentralized WaterThis work was supported by the National Decentralized WaterResources Capacity Development Project (NDWRCDP) withResources Capacity Development Project (NDWRCDP) withfunding provided by the U.S. Environmental Protection Agencyfunding provided by the U.S. Environmental Protection Agencythrough a Cooperative Agreement (EPA No. CR827881through a Cooperative Agreement (EPA No. CR827881--0101--0)0)with Washington University in St. Louis. These materials havewith Washington University in St. Louis. These materials havenot been reviewed by the U.S. Environmental Protectionnot been reviewed by the U.S. Environmental ProtectionAgency. These materials have been reviewed byAgency. These materials have been reviewed byrepresentatives of the NDWRCDP. The contentsrepresentatives of the NDWRCDP. The contentsof these materials do not necessarily reflect the views andof these materials do not necessarily reflect the views andpolicies of the NDWRCDP, Washington University, or the U.S.policies of the NDWRCDP, Washington University, or the U.S.Environmental Protection Agency, nor does the mention of tradeEnvironmental Protection Agency, nor does the mention of tradenames or commercial products constitute their endorsement ornames or commercial products constitute their endorsement orrecommendation for use.recommendation for use.CIDWT/University DisclaimerCIDWT/University DisclaimerThese materials are the collective effort of individuals fromThese materials are the collective effort of individuals fromacademic, regulatory, and private sectors of theacademic, regulatory, and private sectors of theonsite/decentralized wastewater industry. These materials haveonsite/decentralized wastewater industry. These materials havebeen peerbeen peer--reviewed and represent the current state ofreviewed and represent the current state ofknowledge/science in this field. They were developed through aknowledge/science in this field. They were developed through aseries of writing and review meetings with the goal of formulatiseries of writing and review meetings with the goal of formulatingnga consensus on the materials presented. These materials do nota consensus on the materials presented. These materials do notnecessarily reflect the views and policies of University ofnecessarily reflect the views and policies of University ofArkansas, and/or the Consortium of Institutes for DecentralizedArkansas, and/or the Consortium of Institutes for DecentralizedWastewater Treatment (CIDWT). The mention of trade names orWastewater Treatment (CIDWT). The mention of trade names orcommercial products does not constitute an endorsement orcommercial products does not constitute an endorsement orrecommendation for use from these individuals or entities, norrecommendation for use from these individuals or entities, nordoes it constitute criticism for similar ones not mentioned.does it constitute criticism for similar ones not mentioned.CitationCitationKenimer, Ann L., J.Kenimer, Ann L., J.VilleneuveVilleneuveand S.and S.SheldenShelden..2005. Fundamental Concepts: Sedimentation2005. Fundamental Concepts: Sedimentation--Power Point Presentation.Power Point Presentation.inin(M.A. Gross and(M.A. Gross andN.E. Deal, eds.) University CurriculumN.E. Deal, eds.) University CurriculumDevelopment for Decentralized WastewaterDevelopment for Decentralized WastewaterManagement. National Decentralized WaterManagement. National Decentralized WaterResources Capacity Development Project.Resources Capacity Development Project.University of Arkansas, Fayetteville, AR.University of Arkansas, Fayetteville, AR.SedimentationSedimentationSedimentationSedimentationis the gravitationalis the gravitationalaccumulation of solids at the bottom of aaccumulation of solids at the bottom of afluid (air or water)fluid (air or water)Types of SettlingTypes of SettlingFour types of sedimentation:Four types of sedimentation:Discrete settlingDiscrete settlingFlocculant settlingFlocculant settlingHindered settlingHindered settlingCompressionCompressionExamples of Settling TypesExamples of Settling TypesDiscreteDiscreteFlocculantFlocculantHinderedHinderedTypes of SedimentationTypes of SedimentationInIndiscrete settlingdiscrete settlingindividual particlesindividual particlessettle independentlysettle independentlyIt occurs when thereIt occurs when thereis a relatively lowis a relatively lowsolids concentrationsolids concentrationTypes of SedimentationTypes of SedimentationInInflocculantflocculantsettlingsettling, individual, individualparticles stickparticles sticktogether intotogether intoclumps called flocsclumps called flocsThis occurs whenThis occurs whenthere is a greaterthere is a greatersolids concentrationsolids concentrationand chemical orand chemical orbiological reactionsbiological reactionsalter particlealter particlesurfaces to enhancesurfaces to enhanceattachmentattachmentTypes of SedimentationTypes of SedimentationInInhindered settlinghindered settling,,particleparticleconcentration isconcentration isgreat enough togreat enough toinhibit waterinhibit watermovementmovementWater must move inWater must move inspaces betweenspaces betweenparticlesparticlesTypes of SedimentationTypes of SedimentationCompressionCompressionsettlingsettlingoccursoccurswhen particleswhen particlessettle bysettle bycompressing thecompressing themass belowmass belowSedimentation RateSedimentation RateStoke’s LawStoke’s LawUsed for spherical particlesUsed for spherical particlesAssumes no fluid mixing, so usually will notAssumes no fluid mixing, so usually will notwork for gasseswork for gassesµρ−ρ=18)(wpgdv2pSedimentation RateSedimentation Ratevdgp2=−()ρρµpw18vvpp= particle settling velocity (= particle settling velocity (mm//ssororftft//ss))ρρpp= particle density (= particle density (kgkg//mm33ororlblb//ftft33))ρρww= fluid density (= fluid density (kgkg//mm33))d = particle diameter (m or ft)d = particle diameter (m or ft)g = gravitational acceleration (9.81g = gravitational acceleration (9.81mm//ss22or 32.2or 32.2ftft//ss22))µµ= dynamic viscosity (Ns/m= dynamic viscosity (Ns/m22or lbs/ftor lbs/ft22))ApplicationsApplicationsStoke’s Law can be used to determine theStoke’s Law can be used to determine thesurface area of a settling tanksurface area of a settling tankSet the critical velocity equal to the settlingSet the critical velocity equal to the settlingvelocity of the smallest particlevelocity of the smallest particleThe overflow rate is equal to the flow rate intoThe overflow rate is equal to the flow rate intothe tank divided by the surface areathe tank divided by the surface areaSetting the overflow rate equal to the criticalSetting the overflow rate equal to the criticalsettling velocity allows time to capturesettling velocity allows time to capturesmallest particles of interestsmallest particles of interestApplicationsApplicationsOFRvQAc==OFR = over flow rate (OFR = over flow rate (mm//ssoror ftft//ss))vvcc= critical settling velocity (= critical settling velocity (mm//ssororftft//ss))Q = the flow rate into the basin (Q = the flow rate into the basin (m3m3//ssor cfs)or cfs)A = the surface area of the basin (mA = the surface area of the basin (m22or ftor ft22))